 JEE Mains Previous Years Questions with Solutions

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1

AIEEE 2007

In gamma ray emission from a nucleus
A
only the proton number changes
B
both the neutron number and the proton number change
C
there is no change in the proton number and the neutron number
D
only the neutron number changes

Explanation

There is no change in the proton number and the neutron number as the $\gamma$ - emission takes place as a result of excitation or de-excitation of nuclei. $\gamma$-rays have no charge or mass.
2

AIEEE 2007

If ${M_O}$ is the mass of an oxygen isotope ${}_8{O^{17}}$ , ${M_p}$ and ${M_N}$ are the masses of a proton and neutron respectively, the nuclear binding energy of the isotope is
A
$\left( {{M_O} - 17{M_N}} \right){C^2}$
B
$\left( {{M_O} - 8{M_P}} \right){C^2}$
C
$\left( {{M_O} - 8{M_P} - 9{M_N}} \right){C^2}$
D
${{M_O}{c^2}}$

Explanation

Binding energy

$= \left[ {Z{M_p} + \left( {A - Z} \right){M_N} - M} \right]{c^2}$

$= \left[ {8{M_p} + \left( {17 - 8} \right){M_N} - M} \right]{c^2}$

$= \left[ {8{M_p} + 9{M_N} - M} \right]{c^2}$

$= \left[ {8{M_p} + 9{M_N} - {M_O}} \right]{c^2}$
3

AIEEE 2006

The energy spectrum of $\beta$-particles [ number $N(E)$ as a function of $\beta$-energy $E$ ] emitted from a radioactive source is
A B C D Explanation

The range of energy of $\beta$-particles is from zero to some maximum value.
4

AIEEE 2006

The $'rad'$ is the correct unit used to report the measurement of
A
the ability of a beam of gamma ray photons to produce ions in a target
B
the energy delivered by radiation to a target
C
D
the rate of decay of radioactive source

Explanation

The risk posed to a human being by any radiation exposure depends partly upon the absorbed dose, the amount of energy absorbed per gram of tissue. Absorbed dose is expressed in rad. A rad is equal to $100$ $ergs$ of energy absorbed by $1$ gram of tissue. The more modern, internationally adopted unit is the gray (named after the English medical physicist $L.$ $H.$ Gray); one gray equals $100$ rad.